35 (#71) ############################################## CARDING AND CONDENSING General Consideration However well wool may be scoured it invariably appears as a sullied mass after carding. This is specially noticeable in the carding of combing wools (scoured only). It is not that the card dirties the wool, but that certain fibre-groups have emerged from the scouring bath still stuck together by grease and dirt, and the carder, in freeing these, releases a certain amount of grease and dirt which spreads itself over the whole mass and thus gives rise to the sullied appearance of the sliver or film produced. It is just this freeing of the material, fibre by fibre, that carding is designed to effect. It is almost of equal importance that fibres should be reversed and turned about during the passage through the machine-root to tip and tip to root. An excellent training in imaginative insight is to follow a fibre or lock of wool through the card, estimating its chance of being turned round at each roller and averaging up the final result of a number of fibres similarly treated. Mr. Howard Priestman, at Leeds University some time ago, obtained fairly exact results of such a test by tinting the tips of fibres red, passing these into the card under three conditions and then examining the position of each fibre in the resultant sliver.* The cleansing from impurities of the material to be carded is well understood by the cotton carder, but too frequently partially overlooked by the woollen carder. This is due to the comparative unimportance of the cleansing operation in woollen carding as compared with cotton carding, and also to the fact that if the woollen card is properly designed impurities fall out and con- sequently do not involve any special setting of the card, *"Wool Combing," by Howard Priestman, p. 101. » 35